Genesis 22:9-13

And they came to the place which God had told him of; and Abraham built the altar there, and laid the wood in order, and bound Isaac his son, and laid him on the altar, upon the wood. And Abraham stretched forth his hand, and took the knife to slay his son. And the angel of Jehovah called unto him out of heaven, and said, Abraham, Abraham: and he said, Here am I. And he said, Lay not thy hand upon the lad, neither do thou anything unto him; for now I know that thou fearest God, seeing thou hast not withheld thy son, thine only son, from me. And Abraham lifted up his eyes, and looked, and, behold, behind him a ram caught in the thicket by his horns: and Abraham went and took the ram, and offered him up for a burnt-offering in the stead of his son.